Reactive oxygen species induce phosphorylation of serine 118 and 167 on estrogen receptor alpha.
Estrogen receptor alpha (ERalpha) is a well-known target for signaling pathways originating from growth factor receptors. Reactive oxygen species (ROS) can induce activation of extracellular response kinase 1/2 (Erk1/2) and protein kinase B (Akt). Both kinases have been implicated in the phosphorylation of serine 118 and serine 167 on ERalpha, respectively. This activity may lead either to ligand-independent activation of ERalpha or down-regulation of ERalpha and may contribute to development of the resistance to endocrine therapy. Treatment of MCF-7 human breast cancer cells with glucose oxidase (GO, 0.1 un/ml) induced transient phosphorylation of serine 118 and serine 167. The increase in expression of p-ser118-ERalpha was 355 +/- 98% (mean +/- SD) and of p-ser167-ERalpha was 632 +/- 355%. These effects were enhanced in Her2 over-expressing MCF7 cells. ERalpha expression declined to 63 +/- 20% within the first 90 min of treatment and was below 10% 24 h later. ROS induced phosphorylation of ERalpha resulted in decreased expression of pS2 and progesterone receptor. Activation of Erk1/2 and Akt was transient with highest levels of Erk1/2 being 595 +/- 143% and p-Akt 311 +/- 125%. Inhibition of Erk1/2 by U0126 (10 microM) decreased p-ser118-ERalpha by 51.7 +/- 8.5% and decreased p-ser167-ERalpha by 41.9 +/- 16.9% whereas inhibition of Akt by LY294002 (20 microM) and wortmannin (500 nM) or by siRNA knock-down, had no effect on p-ser167-ERalpha expression. Our data show for the first time that ROS can induce post-translational modifications of ERalpha at serine 118 and serine 167, and may lead to ERalpha down-regulation in human breast cancer cells. Both the phosphorylation and consequent down-regulation of ERalpha may be a mechanism associated with development of endocrine therapy resistance.
Weitsman
Gregory E
GE
Manitoba Institute of Cell Biology, University of Manitoba, 675 McDermot Ave, Winnipeg, MB, Canada R3E 0V9.
Weebadda
Wineeta
W
Ung
Kanyarat
K
Murphy
Leigh C
LC
D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D015536:Down-Regulation; D047628:Estrogen Receptor alpha / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species / Q000378:metabolism*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D014162:Transfection
D047628:Estrogen Receptor alpha; D048049:Extracellular Signal-Regulated MAP Kinases; D051057:Proto-Oncogene Proteins c-akt; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D018719:Erb-b2 Receptor Tyrosine Kinases; D012694:Serine